Field of Invention
The present invention relates to a light source assembly. More particularly, the present invention relates to a light source assembly and its fabrication method by welding to fix a light bar on a back plate.
Description of Related Art
Referring to FIG. 1 and FIG. 2, FIG. 1 is a schematic diagram showing a conventional process of welding a light bar 110 on a back plate 130, and FIG. 2 is a schematic structural diagram showing the conventional light bar 110 welded on the back plate 130. In the conventional backlight module, the light bar 110 is directly welded on the back plate 130. Before the welding process is performed, a light bar 110 is directly placed on a back plate 130 to enable a bottom surface 110a of the light bar 110 to be in completely contact with a surface 130a of the back plate 130. Thereafter, the welding process starts from a edge 150 between a back surface 110b of the light bar 110 and the surface 130a of the back plate 130 by using a welding device 190, so as to fix the light bar 110 on the back plate 130.
As shown in FIG. 1, in the welding process, a heat-conducting area A1 of the light bar 110 is quarter-circular, and a heat-conducting area A2 of the back plate 130 is semi-circular, meaning that the heat-conducting paths of the light bar 110 and the back plate 130 have different lengths and ranges, thus resulting in that the thermal stresses exerted on the light bar 110 and the back plate 130 are not uniform. Moreover, during the welding process, a peripheral position around the edge 150 is heated and melted firstly, causing the light bar 110 to be inclined to the back plate 130 (as shown in FIG. 2) instead of being upright thereon, or causing the back plate 130 to have irregular warpages, and thus the difficulty of the welding process is increased, and the welding quality and the whole optical efficiency of the backlight module are affected.
In addition, as shown in FIG. 2, after the welding process is completed, a welding layer 170 is formed between the bottom surface 110a of the light bar 110 and the surface 130a of the back plate 130. One of the major functions of the welding layer 170 is to transfer the heat generated by the light bar 110 to the back plate 130 and further to the ambience. Therefore, the depth D1 of the welding layer 170 can represent a depth of effective heat-conduction range. In other words, a larger depth D1 of the welding layer 170 stands for a larger area of the welding layer 170, and the heat conduction effect is better. However, if the depth D1 is desired to be deeper, the welding process requires much more energy. However, as shown in FIG. 1, during the welding process, the light bar 110 and the back plate 130 will undergo extremely high temperature at first. When the depth D1 is increased during the welding process, the desired energy and temperature is increased accordingly, and thus the damage of the light bar 110 due to too high temperature is likely to be caused.